About: After being laid off in 2009, I got rid of my car to save money. The difficult transition from a car to a bicycle led me to start Solarcycle and design USB chargers that keep smart phones alive.
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This Instructable introduces a new Open Source USB rechargeable soldering iron called Solderdoodle Plus. Twice as powerful as the original Solderdoodle, it features 10 Watts of adjustable power with touch control, LED status indicators, and can truly replace a corded device. Swipe to adjust power and press down to activate heat. Safety features include a sleep mode that disables the unit when not in use, low battery warning, and a dual-cell battery charge controller.

Solderdoodle Plus can last over 1 hour with constant maximum power at 500 Degrees C.

You can literally go anywhere and still have a way to charge your Solderdoodle Plus if there is a laptop, USB battery, wall adapter, or even a USB solar charger nearby! Alternatively, you can use the Solderdoodle Plus as a corded device, which means it can charge and discharge at the same time.

* Battery Life Under Typical Use: 5-10 years until battery capacity significantly decreases

* Provides 1 hour of continuous heat at full power * Heats up to over 572ºF (300ºC) in just 15 seconds

*WARNING: Be careful when handling any Lithium-Ion battery because shorting the battery can cause burns. Always wear safety goggles. Please use recommended battery and circuit components because of the higher 2500mA max battery charge current involved. 3D printed parts may warp under high temperatures. This is only a prototype so there may be performance issues that have not been fixed yet.

Step 2: Heating Element and Power Cable Assembly

(Optional: Remove the heating element) Unscrew the Weller soldering iron, remove all the parts, and just keep the heating element assembly. Desolder the coiled wire and LED cable from the heating element. Use the Dremel tool with the diamond point bit to grind the area around and inside the tiny hole where the switch spring attached in order to remove the plating for soldering and increase the hole size a little.

Cut a 1-1/8" length of the red and black wire. Strip .06" off both ends of the red wire and put one end inside the tiny hole. Use a third hand clamp for easier soldering. The silicone jacket is very flexible so you can slide the jacket back if you need to expose more wire temporarily. Use flux and then solder the wire in the tiny hole with just a little wire sticking out the other side for the solder to flow. Next strip .06" of one end of the black wire and .2" off the other. Soldering the .2" stripped end to the center cup of the tip connector. Crimp the connector to the other ends of the wire and connect the 2-Pin connector to the wires as shown in the photo (Pin 1: RED, Pin 2: Black).

Cut 3-3/8" length of the black and three red wires. Strip .06" off both ends of all these wires and crimp connectors on each end. Connect the wires as shown in the photo and in the pin list below:

2X2 Connector TO 4X1 Connector

Pin 1: Red -----> Pin 4

Pin 2: Black -----> Pin 3

Pin 3: Red -----> Pin 2

Pin 4: Red -----> Pin 1

Remove the soldering tip at this point for safe installation in the final steps.

Step 3: Solderdoodle Plus Programming

The following is a tutorial on how to download the control software to the Solderdoodle Plus Controller Board. You don't have to use the same exact parts and most likely if you have any type of breadboard and a Teensy 3.2 or 3.6, you can find spare parts laying around to wire things up. Attached on the first page of this Instructable is the Solderdoodle Plus Arduino sketch and a schematic for reference. The LEDs and resistors don't have to be exact because they are just to double check that the programmer is communicating. You can use an Arduino board too, but you would need to change some settings.

The Solderdoodle Plus Control Board has 2X3 through hole vias in the corner with .1" spacing for programming the Attiny84A. I used pogo pins attached to 2 custom cut proto board pieces and soldered in place. The cable is just thin flexible wire with D-SUB high density female pins crimped and heat shrunk on one end and male D-SUB high density pins crimped on the other end connecting to the breadboard. If you don't have these, you could try just poking wires or pins through the via, then put a little side pressure to make sure the wires or pins make contact with the programming vias.

FLASH THE TEENSY PROGRAMMER

0. Double check to make sure you have the latest Arduino software DON'T USE MICROSOFT STORE (Installing with Microsoft Store on Windows puts the program in a secure folder that Teensy cannot access).

1. Install Teensyduino (Even if you think you already have this, check again for the latest version):

6. If you're using a brand new Solderdoodle Plus Controller Board, use this tool before going further: ­

Tools ­> Burn Bootloader

This should fix the clock speed on the chip.

7. Finally: Click the "Upload" button to flash the ATtiny chip. The LEDs should blink, the Sketch window should say upload complete, and you're done!

SYSTEM CHECK

Plug in the power cable to the Solderdoodle Plus Dual Charge Control Board and attach it to the Solderdoodle Plus Control Board. Flip the power switch on, and try out the touch sensor to make sure it is working properly before continuing. If it's working properly, flip the power switch off and disconnect the power cable from the Solderdoodle Control Board.

Step 4: Solderdoodle Plus Assembly

Now for the final steps in the Assembly! First be aware that the 3D printed parts are not precise, so check to see how each part fits before continuing on with the assembly. You may have to use a hobby knife to scrape away a little material if the fit is too tight, especially around the heating element assembly cavity. I think the black color is added paint that adds a little thickness too.

Second, take the Solderdoodle Controller Board by itself and press in the press fit LED light pipes. If there is a little gap and it doesn't slide all the way down that's ok.

Third, attach the touch sensor cable in the orientation shown in the photo.

Fourth, install the batteries in to the Dual Charge Control Board battery clips making sure that the positive ends of the batteries go in to clips labeled BAT1 and BAT2.

Fifth, attach the power cable, Dual Charge Controller Board, and Heating Element Cable to the Solderdoodle Control Board. Make sure the power cable twists around in the direction shown in the photo.

Sixth, make sure the protective backing of the touch sensor is removed and place the entire board and cable assembly in to Side A 3D printed case with the touch sensor going in first. Make sure that the touch sensor cables folds exactly like it's shown in the photo. If the fit is too tight, especially with the USB connector, remove and trim excess plastic with a hobby knife and try again. The Solderdoodle Control Board has a notch that should fit around the mating plastic tab inside Side A. Push the wires in to place in order to remove any springiness and twisting the assembly. If needed, place a piece of tape to hold the assembly steady in the case.

Seventh, this might be the more tricky part in the assembly, but attach the Side B 3D printed case to Side A while making sure the circuits inside don't move. Attaching the heating element assembly first seems to be the best method while making sure the touch sensor slides in the mating cavity and the LED light pipes are going through the holes at the top. The sensor cable wire conductive traces can be scratched off so be careful that minimal rubbing or scraping on the cable occurs during assembly. Make sure everything seats properly by making sure the touch sensor isn't bent or buckled and that there are no major gaps in the seams or parts sticking out. If you have to poke inside the case while assembling, make sure you poke with a plastic or non-conductive tool as poking with a metal object can cause a short.

Eighth, while holding Side A and B together, insert the 4 screws and screw them in. If you'd like to make the "Solderdoodle Plus" text on the case stand out more, simply paint the raised text with a contrasting color. Before attaching the soldering tip, turn the power on and check to make sure the touch control is working. Swipe up and down to adjust the power and push down on the sensor to activate heat. Also, triple tap the sensor to put in sleep mode and triple tap again to wake. Sleep mode is automatically activated after 5 minutes of idle.

CONGRATULATIONS! Your done building Solderdoodle Plus! Now you can attach the soldering tip and go solder!

Step 5: Safety and Troubleshooting

LIVE STREAM DEMONSTRATION ABOVE

This temperature test shows that the quality of Solderdoodle Plus is very high. However, this is only a prototype version so there may be issues with performance that have not been fixed yet.

Solderdoodle Plus only turns on by swiping on the sensor and then pressing down on the sensor, so I put a heavy weight down on the sensor and let it run with a temperature probe touching the tip. I took photos of the test and plotted it in a chart, which is shown above. You can see that the temperature is around 500 Deg C for over an hour at maximum power. The software shuts off the system when the battery pack voltage drops below 6.1 Volts. Under normal use, the power button isn't held down this long, so it should last much longer during normal use.

Solderdoodle Plus’ battery pack uses a charge controller on each cell. Each charge controller is on an isolated ground, ensuring each cell charges independently and never goes beyond the maximum and minimum voltage, which allows the cells to last 5 to 10 years before needing to be replaced.

SAFETY

Do Not leave Solderdoodle Plus in direct sunlight. Keep it covered or in the shade. Heat from the sun can cause the charge circuit and battery to get very hot, stop charging, degrade the battery, and shorten its lifespan.

Acceptable Operating Temperatures: Solderdoodle Plus is designed to be operated in temperatures between 0º and 45º C (32º and 149º F).

Storage: Switch the power off, remove the tip, and store Solderdoodle Plus in room temperature. Solderdoodle Plus should be recharged about once a year to prevent over discharge.

2) Disconnect the touch sensor and make sure the connector and cable are clean and have no obstructions.

2) Remove touch sensor from plastic case and reinstall to make sure sensor is seated correctly all the way in the slot. Any bends or kinks in the touch sensor will prevent the sensor from working properly.

Charge LEDs don't light up when charging from my laptop:

1) This can occur if Solderdoodle Plus is completely drained and goes in to a trickle charge mode. Keep Solderdoodle plugged in for about 15 minutes and the LED charge lights should turn back on.

2) Some older laptops have a low current limitation in their USB ports and will disable the USB port if the current exceeds the limit. Try plugging Solderdoodle in to another USB port or higher current USB wall adapter.